Braun tube and method of producing the same



1937. K. SCHLESINGER BRAUN TUBE AND METHOD OF PRODUCING THE SAME Filed July 6, 1934 Unvenl'oc: mfw I Patented Nov. 30, 1937 UNITED STATES BRAUN TUBE AND METHOD OF PRODUCING THE SAME Kurt Schlesinger, Berlin, Germany Application July 6, 1934, Serial No. 733,996 In Germany July 10, 1933 11 Claims.

The Braun tubes known up to now having a greater picture receiving screen in the order of 10x 12 cm. or more possess a cylindrical neck and a frusto-pyramidal bulb closed by a bottom which is made as fiat as possible and in the majority of cases acts itself as support for the luminous screen. In these known tubes the bottom of the bulb is subjected to a comparatively strong tensile strain both at the center as well as more particularly along the line of connection between the bottom of the bulb and the bulb body. In the case of relatively large tubessuch as are necessary more particularly for television purposesthis form of bulb frequently results in implosion.

The object of the invention is a Braun tube having a picture receiving screen in the order of more than 15X15 cm., and also a method of producing the same, in which complete proof against implosion is ensured in spite of the great size of the tube.

According to the invention, the bulb of the Braun tube is constructed on such lines that tensile strains are unable to take place at all or only to a very small extent.

The tube according to the invention may preferably be constructed as a spherical body furnished with a cylindrical neck portion.

If a greater length of bulb is desired, the spherical body may be replaced by a body which consists of two spherical sections with an intermediate cylindrical portion located between the same. In this case the elevation, i. e., the distance between the center of the bottom of the sphere a and the center of the upper cylinder plane must amount to, at least 7 cm. in the case of a cylinder diameter of cm. or more. With a diameter of the cylinder amounting to 34 cm. the elevation will preferably be approximately 10-12 cm.

The fluorescent substance may preferably be provided on a plane parallel sheet of glass, which is secured within the bulb, preferably in the vicinity of the bottom thereof.

The attachment of this support for the luminous screen-which may be constructed as a very thin sheet of glass (for example, 0.5-1 mm.) may take place, for example with the use of resilient distance pieces, which engage in corresponding recesses or contractions in the bulb or about elevations provided for this purpose.

It is particularly convenient, however, according to the invention to secure the luminous screen by means of one or more resilient rings (pressv rings).

As resilient rings there may conveniently be employed rings composed of material well capable of being outgassed but not resilient in itself, for example phosphor bronze, which rings are pressed apart by means of a spring fitted at a suitable point.

It is possible to furnish attachment means on a ring of this nature, and to mount the support for the luminous screen on these attachment means.

On the other hand it is possible to provide two resilient rings of this nature and to arrange the support for the luminous screen-between the 7 same, there preferably being furnished between the edges of the support for the luminous screen (if the same is not formed as a circular disc) and the wall of the bulb a resilient intermediate layer, which preferably is connected with one of the rings.

For television purposes there are employed at the present time on the one hand gas tubes and on the other hand high vacuum tubes. The

example, to within 2-3 cm.) with the length of the system, so that the total of the system may be arranged in this neck, and the total length of the tube, i. e., the total derived from the length of the neck of the bulb and of the tube bulb is practically the same in all cases, i. e., both in thecase of gas tubes as well as high vacuum tubes.

For both forms of tube it is possible in accordance with the invention to take the same basic form of bulb, which possesses both the maximum neck occurring as well as the maximum length of bulb. For gas tubes a part of the neck of the bulb is cut away, for'high vacuum tubes the neck of the bulb remains unaltered andupon the fitting of the support for the luminous screen-a part of the cylindrical intermediate portion of the bulb may be removed.

Several forms of embodiment of the bulb according to the invention are illustrated by way 0 example in the drawing, in which Fig. 1 shows the basic form of the bulb (having a bulged portion for holding the luminous screen). 7

Fig. 2 shows a bulb for high vacuum tubes, the body of which bulb is shortened during the fitting operation, whilst in Fig. 3 there is shown a bulb having a luminous screen held by means of springs engaging in the bulged portion, whilst Fig. 4 shows a tube having a luminous screen held by a single press ring.

Fig. 5 shows a tube, in which the luminous screen is held by two press rings.

The method, according to the invention, may be performed as follows 2 In the first place there is produced in the manner known per se the axially symmetrical bulb comprising the cylindrical neck portion 2, the two spherical parts I and 3, and the cylindrical middle portion II,

This bulb is held preferably at the nepk in a suitable device, and rotated about its axis at an even speed. The bulb is thereupon scored by a suitable device along the line A--B, and if desired along the line BO, and the two scored lines subjected to a sudden jump in temperatu e, so that co l y re ular ou dge r formed along the on or oss bl a ne he two straight lines. The luminous screen is thereupon fitted, as described later, and the body of the bulb is again fused together to form a whole, in the case of gastubes along the line AB and in the case ofhigh vacuum tubes along the lines A.,B and B O, by simultaneous rotation of the two parts of the bulb, which preferably are pressed sharply together. 7

The fusing .line may conve n be disposed in all cases as far away as possible from the luminous screen. As shown in Fig. 3, the support 6 carrying the fluorescent substance 5 .may be furnished with a mounting 1 consisting, for example, of phosphor bronze, on which mounting there are secured resilient parts 8, which are fitted into the recess 9 in the glass bulb and hold the screen inimmovable fashion. Thenum ber of resilient members 8 distributed along the metallic mounting I may be selected as desired, for example may be 4-42 in number.

As shown in Fig. 4, it is also possible to secure the luminous screen within the glass bulb without necessity for particularly deforming the bulb (grooves or the like).

In. the body l2 of the bulb, as far as possible at the. end .of the cylindrical portion in the vicinity of, the spherical portion 3, there is fitted a press ring, which may consist, for example, of the non-resilient metal ring l3, pressed apart. by the spring l4 and furnished with abutments l5. Generally the term press ring (or spring ring) is intended to mean a ring member being pressed against the glass wall and being held in its position by this pressure without the use of additional holding means. The image screen 6 is secured to the abutments 15 in suitable fashion (for example by welding a metallic mounting to. the holding. means l5).

As indicated in Fig. 5, it is also possible to arrange the image screen 6 between the two press rings [6 and I1.

The two forms of embodiment last described have the advantage that every deformation of the tube body which might result in a weakening of the tube, and accordingly in an increased danger of implosion, is safely avoided.

c Since in the tube according to the invention the luminous screen is produced outside of the bulb, it is possible to make use of the sedimentation process, and in this way to produce luminous screens of a considerably more regular nature.

The method according to the invention enables for the first time Braun tubes to be produced, completely secure against implosion, for the production of television images of large size, which tubes in an optical respect are at least equivalent to the known tubes.

I claim:

1. A cathode ray tube fer television purposes comprising an image receiving screen, said image receiving screen having an area of at least fifteen times fifteen cm., an envelope having a curved end portion and wherein the radius of curvature of the end portion of the envelope is substantially constant throughout the curved end portion, and means for secur-,

ing said image receiving screen within said envelope, said means including a metal ring pressed against the inner wall of said envelope, and means for firmly connecting said image receiving screen with said metal ring.

2. A cathode ray tube for television purposes comprising an image receiving screen, said ima re e v creen h vin an are of at least fifteen times fifteen cm., an envelope having a curved end portion and wherein the radius of curvature of the end portion of the envelope is substantially constant throughout the curved end portion, means for securing said image receiving screen within said envelope, said means comprising a non-resilient metal ring, a spring pressing said metal ring against the glass wall of said envelope and means for firmly connecting said image receiving screen to said metal ring.

3. A cathode ray tube for television purposes comprising an image receiving screen, said image receiving screen having an area of at least fifteen times fifteen cm., an envelope having a curved end portion and wherein the radius of curvature of the end portion of theenvelope is substantially constant throughout the curved end portion, and means for securing said image receiving screen within saidenvelope, said means comprising a deformation in the body of said envelope, a metallic frame surrounding said image receiving screen, and a plurality of springs connected to said metallic frame and secured to said deformation.

4. In the method of producing a Braun tube having an envelope with a curved end portion the steps of splitting the envelope up into two parts, inserting a spring ring, securing a fiuores cent screen to said ring and fusing the split up parts; together.

5. In the method of producing a Braun tube having an envelope with a curved end portion the steps of splitting a Braun tube envelope by two cross-sections into three parts, removing the middle one of said three parts, inserting a spring ring into one of the two remaining ones of said three parts, securing a fluorescent screen to said ring, and fusing the two remaining ones of said three parts together.

6. A cathode ray tube for television purposes comprising an envelope having a curved end portion and wherein the radius of curvature of the end portion of the envelope is substantially constant throughout the curved end portion, an image receiving screen, and means for securing said image receiving screen within said envelope, said means comprising a non-resilient metal ring, a spring pressing said metal ring against the glass wall of said envelope, and means for firmly connecting said image receiving screen to said metal ring. 7

'7. A cathode ray tube for television purposes comprising an envelope having a curved end portion and wherein the radius of curvature of the end portion of the envelope is substantially constant throughout the curved end portion, an image receiving screen, and means for securing said image receiving screen within said envelope, said means comprising a deformation in the body of said envelope, a metallic frame surrounding said image receiving screen, and a plurality 'of springs connected to said metallic frame and engaging against said deformation.

8. A cathode ray tube for television purposes comprising an envelope having a curved end portion and wherein the radius of curvature of the end portion of the envelope is substantially constant throughout the curved end portion, an image receiving screen, and means for securing said image receiving screen within said envelope, said means comprising a ring shaped spring member firmly engaging due to its elasticity against the wall of said envelope, and means for firmly connecting said image receiving screen to said ring shaped spring member.

9. A cathode ray tube for television purposes comprising an envelope having a curved end portion and wherein the radius of curvature of the end portion of the envelope is substantially constant throughout the curved end portion, an image receiving screen, and means for securing said image receiving screen within said envelope, said means comprising two ring-shaped spring members mounted adjacent to, and axially aligned with, each other within said envelope and firmly engaging, due to their elasticity, against the wall of said envelope, said screen being disposed between said two members and so supported in position.

10. An envelope for Braun tubes for television purposes comprising a cylindrical portion having a diameter of at least 30 centimetres, two curved portions each attached to one end of said cylindrical portion so as substantially to close off said cylindrical portion at the end to which said curved portion is attached, each of said curved portions having the shape of a part of a hollow sphere facing said cylindrical portion with its concave side, the apex of one of said curved portions having a distance from the virtual base of said curved portion which is at least equal to 7 centimetres, the other one of said curved portions having an opening at its apex, a neck-portion secured to the edge of said opening in a position co-axial with said cylindrical portion, and a picture receiving screen attached to said cylindrical portion at the inside thereof.

11. An envelope for Braun tubes for television purposes comprising a cylindrical portion having a diameter of at least 30 centimetres, two curved portions each attached to one end of said cylindrical portion so as substantially to close oiT said cylindrical portion at the end to which said curved portion is attached, each of said curved portions having the shape of a part of a hollow sphere facing said cylindrical portion with its concave side, the apex of one of said curved portions having a distance from the virtual base of said curved portion which is at least equal to '7 centimetres, the other one of said curved portions having an opening at its apex, a neck-portion secured to the edge of said opening in a position co-axial with said cylindrical portion, and a picture receiving screen attached to the first said curved portion.

KURT SCI-ILESINGER. 

